Measuring and recording apparatus



Je/Jm ome fer W. H. MAYNE MEASURING AND RECORDING APPARATUS Original Filed June 1, 19.40

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MEASURING AND RECORDING APPARATUS Original Filed June 1, 1940 2 Sheets-Sheet 2 ascent asnnmc ann nnoonnrna area William H. Mayne, San Antonio, 'len, asslgnor to @live S. Petty, San Antonio, 'leir.

Original application lane 1, i940, Serial No. 3%, lld. Divided and this application .l'une 2d, 1941, Serial No. 399,55t

l @lalm.

This invention relates to apparatus and methods for use in electrical circuits and is particularly concerned with circuits adapted to be supplied with wave form electrical energy. It is one of the objects of the invention to provide a novel and emcient means for measuring and/or recording electrical energy.

It has heretofore been proposed to employ thermionic valve circuits in the measurement of small voltages, and particularly of alternating voltages. Such arrangements have, however, been subject to various well recognized defects which it is the object of the instant invention to overcome.

Thus I have discovered that the characteristics of a thermionic valve of conventional type may be so adjusted by suitable selection of the voltages applied to the various elements of the valve that the relationship between the grid voltage and the anode current can be caused to assume ject of the invention to provide, in combination with a thermionic valve circuit adjusted as described, measuring means such as a DArsonval galvanometer for the valve output, whereby eflective values or the applied grid voltage may be indicated directly and independently of the wave form. Still a further object or the invention is to provide, in association with such a valve, measuring means such as a recorded oscillograph for tracing the full wave squared curve of the control voltage applied to the valve grid.

The invention also contemplates the application of a thermionic valve circuit adjusted as described to any field in which it is desired to raise wave form electrical energy to the second or higher power. Thus the circuit may be employed in the field of seismic surveying, in which seismic impulses are converted into electrical wave form energy for subsequent recording, the squaring of the energy serving the purpose of exaggerating larger impulses on the record at the expense of smaller impulses, for example stray and unwanted impulses. As a modification of the invention,

specifically applicable to the field of seismic surveying, I propose to employ, in lieu of the thermionic valve circuit in question, some other type of device for squaring the energy derived from seismic impulses. The instant application is particularly directed to these and other related adaptations of the invention to seismic exploration and apparatus, other uses and further and broader aspects of the invention being claimed more especially in my prior application Serial No. 838,440, filed June 1, 1940, of which this application is a division.

Further objects and features of the invention will be apparent from the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of an electrical circuit, indicating one method of applying the instant invention to the measurement of pulsating electrical energy;

Figure 2 represents generally the grid voltageanode current curve of the thermionic valve included in the circuit shown in Figure 1;

Figure 3 diagrammatically illustrates the application of the invention to the field of seismic surveying by the use of modified apparatus;

Figures 4 and 5 are characteristic grid voltageanode curernt curves of thermionic valves such as may be employed in the practice of the invention; and

Figure 6 is a circuit diagram illustrating the use of the invention for frequency multiplication.

In order to facilitate an understanding of the invention, reference will be made to the several embodiments thereof illustrated in the accompanying drawings and specific language will be employed. It will nevertheless be understood that various further modifications of the devices illustrated herein, such as would fall within the province of those skilled in the art to construct are contemplated as part of the present invention.

In Figure 1 of the drawings the reference numeral it represents diagrammaticaly a source of electrical energy, for example wave form energy. Thus the source it may be a seismometer for use in seismic surveying, the seismometer serving to convert into electrical wave form energy seismic impulses which may be propagated as the result of detonation of an explosive charge in accordance with methods commonly practiced in this field. The seismometer may be constructed as disclosed more particularly in the application of Olive 8. Petty, Serial No. 324,013, filed March 14,

1940, in'vvhich the seismic impulse are caused to vary the impedance of an oscillating circuit, and thereby the output of the circuit.

Whatever the nature of the source it, it will be understood that there is preferably delivered to the terminals ii and it a varying or pulsating electrical energy which it is desired to measure, record, or otherwise to deal with as hereinafter more particularly described.

From terminals ii and iii, the energy is led to an electrical circuit including a thermionic valve ill, the characteristics of the latter being so ad dusted that the output current or the valve varies substantially as the square or the input voltage. in the preferred practice oi" the invention, the desired result is achieved by appivina, to certain elements of the valve, voltages which are such that the characteristic anode current-grid voltage curve thereof is substantially parabolic over a ranae commensurate with the range oi voltaaes to be supplied to the valve control grid and attending on both sides of the parabolic verter, the valve heme biased to a static operating point at the parabolic vertex.

The valveshouln at it is of the multi-urld type, input terminal ii applying a varying voltage to control arid iii and input terminal it being con nected to the cathode ll of the valve. The valve may also include high voltage grids id and lit, the latter beina" oi the screen type, and a low voltat'e arid which is connected to the cathode throush a variable tap on a source it": oi grid bias voltaae. The latch voltage erids are preferably supplied with biasing voltage through resistances and iln appropriate potential for the control arid it is established by means of a potentiometer connected across the source The anode lid is connected through a variable resistance til to the positive terminal of a source ll of anode voltaae, the negative terminal heme re" turned to the cathode ii. i i measuring and/or recordina device til is arranged in shunt between the anode and the screen arid it so as to illdicate the drop in voltase across the variable resistance and thereby the anode current.

it will be appreciated that in practice it may be necessary to provide amplification of the Wave iorm sianai energy additional to that afiorded by the illustrated circuit, and the invention CDlIItBll'l" the employment oi iurther amplifying stapes at any convenient point in the system.

lll'ie significant ieature oi the illustrated sircult is its ability square the incoming signal eneray. "lhtm the circuit is adjusted, as hereinbefore errplained, to provide an approximately parabolic anode voltaae arid current characteristic, such for example, as is diagrammatically represented in Figure 2. in this iieure, the upper pertion of the curve between. the points a and c is generally parabolic, and the valve it is normally biased so as to establish a static operating point at the parabolic vertezr h. it will thus be apparout that as the voltase applied to the grid it varies between a and c, the anode current will vary as the square oi" that voltase.

it the measuring: instrument is a aalvanometer oi the Dilrsonval type having a long period as compared to the received frequencies, such instrtunent vvili indicate edective values or the arid voltage ivave directly, linearly, and independently oi the i'orm oi the Wave, since the aver one of a squared Wave is the effective value of the oriainal tvave. 'lo standardize the instrument readings it is necessary only to adjust initially the variable resistance fit so that the voltaaoaaae aye applied to the instrument it is within the range of scale readings, then to adjust the potentiometer it so as to bias the valve it for operation at the point it of the voltage-anode current curve, at which point the response of the instrument is at a minimum, and finally to adjust the variable resistance lid so. that the instrument reads zero in the absence oi applied control voltage. By properly calibrating the linear scale of the meter, a reading of the applied signal may he obtained directly in the numerical value of the effective voltaae.

In the use of the invention in certain fields, for example in the field of seismic surveying, it is customary to employ a recording oscillograph, for example a string aalvanometer. The use of such a device at permits the tracing of the squared curve oi the alternating voltage applied to the control grid id of the valve. In this connection it may be noted that the full wave of the applied signal is measured, so that the resultant trace is Wholly independent of Wave form. The errors attendant upon the more conventional hali-vvave rectification by means of a valve biased to cutoff are thus eliminated. Similarly, the present invention gives results definitely superior to those obtained with full Wave circuits employing two valves, such circuits being dimcult of adjustment as regards the point of cutoff and involving other disadvantages which are eliminated by the instant arrangement.

In Figure a is shown a series of curves representina the grid voltage-anode current characteristics of valves of the general type shown in Figure l. The difference in the shape of the several curves is the result of differences in the circuit constants selected, and the generally parabolic shape of all of the curves was obtained by suitable adjustment of the voltages applied to the several elements of the valves, and primarily by the application of a substantially higher voltageto the screen arid it than is normally empioyed. Numerous combinations of voltages which will afford generally parabolic curves errtendinu on each side of the vertex may be emplayed in Widely divergent types of valve. The operating portion of the curve may in some instances be inverted, the vertex being below the adjacent curve sections.

By Way of example, and Without limitation. of the scope of the invention, the following constants Were applied to a valve of the lfi'l-G type, reference being. made to the numerals applied to the elements of the valve shown in Figure 1 for identification of the respective elements:

Volts Grid 16 --d. 8 Grid 19 22. 25 Grid 20 89. Grid 22 -2.9 Anode 28 86.

While valves of the so-called pentagrid. converter type, such as the valves just described, are particularly suited to the practice of the instant invention, various other types of valve may be successfully employed. In general it is desirable to employ a valve having at least three grids, the intended result being achieved by the application of negative bias voltage to the first and third grids, and a relatively high positive voltage to the intermediate grid, preferably through a resistor.

in Figure 5 the upper portion of several of the v5 curves appearing in Figure l is represented on ascents a scale in which the ordinates are expanded. The close approximation of these curves to the parabolic form is at once ,apparent from this figure. The highest curve in Figures 4 and 5 was obtained by the use of the voltages above set iorth.

The circuit hereinbefore described is especially advantageous Where it is desired to measure the effective value or record the instantaneous value of wave form energy with accuracy. In the field of seismic surveying, however, accuracy of representation of wave form is often not essential and it is possible to employ apparatus of less accuracy which will emphasize impulses of higher amplitude by raising the energy to the second or some higher power. Thus reasonably satisfactory results may be achieved in this field by the use of an arrangement such as that illustrated in Figure 3, which employs a meter iii] of the moving coil type, the moving coil ti and the fixed coil t2 being arranged in series. Energy may be supplied to the coils from a conventional thermionic valve amplifier I55, the latter receiving the output of a seismometer it. Alternatively, thermionic valve circuits affording an output which is generally representative of the square of the input voltage may be employed, for example circuits such as are commonly used in voltmeters of the thermionic valve type, the valve or valves being biased to cutoff and having generally parabolic grid voltage-anode current characteristics adjacent'the cutod point.

By the use of two or more of the circuits herein-described in series, higher powers of the applied voltage may be derived. Multiplication of signal energy from different sources by the application oi the instant invention is dealt with more partiticularly in my copending application, herial No. 338.439, filed June 1, 1940.

it will be apparent from Figure 2 of the drawings that the frequency oi the direct current pulsations oi the valve output is twice the ireuuency or alternation of the voltage applied to the control grid. It is therefore possible to derive i'rom the; output current an alternating current which isQa pure second harmonic of the input voltage, for example by the employment of a transformer in the anode circuit of the valve.

Such an arrangement is illustrated in Figure 6 of the drawings, this figure servingalso to illus trate the use of a pentode valve in the practice of the instant invention. The circuit shown in Figure 6 is essentially the same as that represented in Figure l, and similar reference characters are employed to designate identical elements functioning similarly, it being understood that the seismometer output may be applied to the terminals II and 12, as in Figure 1. The valve 33 includes a cathode 37, a control grid 36, a screen grid till, a suppressor grid 32, and an anode d8. A small negative bias is applied to the grids 36 and M by the source and a relatively high positive potential is applied to the screen it] by the source 3| through a resistor ii; source 3i also supplies voltage to the anode it through the primary winding 50 of a transformer 5i, the output of which may be recorded as hereinbefore described on an oscillograph or like recording instrument. The voltages applied to the several elements of the valve are so chosen, as hereinbefore explained, that the grid voltage-anode I current curve is parabolic, the static operating point being located substantially at the vertex of the parabola.

It will be appreciated from the foregoing that the current flow in the secondary winding 52 of the transformer will represent the alternating current component of the valve output, and that this component will vary at a frequency twice that of the original signal. The arrangement is distinctly superior to more conventional circuits for obtaining frequency multiplication, since it is unnecessary to employ elaborate filters for the elimination of undesiredharmonics. The signal frequency can of course be further multiplied, if desired, by feeding the signal successively through a plurality of circuits of the type shown in Figure 6.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

In apparatus for use in seismic'surveying, the combination with a seismometer for converting seismic energy into electrical Wave form energy, of means for amplifying and recording said wave form energy, said recording means including an energy squaring device, said device including a recording oscillograph of the electro-dynamometer type having fixed and movable coils, and means energizing both of said coils with said Wave form energy.

WILLIAM H. MAYNE. 

